Troubleshooting Tip: Using 'route-map-out-preferable' in BGP for route-tag use in an SD-WAN rule

[Kraven2323]

Description	This article describes, with an example, how the 'route-map-out-preferable' functions in the BGP route-tag and is used concurrently with an SD-WAN rule.
Scope	FortiGate.
Solution	Prerequisites: SD-WAN with 'SLA' and 'config neighbor'. See the documentation. BGP with route-map. See the documentation. The scenario below is the route-tag in HUB for the BGP route from Branch when SLA is met: In this scenario, the SD-WAN rule in the HUB was configured to follow the route tagging. Consider the SD-WAN rule for Dialup_1_1, which is meeting the SLA first. In Branch, the route-map is configured to have route-map-out-preferable when SLA is met and route-map-out when SLA is not met. Now, make the Dialup_1_1 fail the SLA from the branch. Note the route-tag for the Dialup_1_1 is changed to 5. Note that the SD-WAN rule will not be matched as the route-tag is not matching. This will cause the traffic to use other SD-WAN rules which match the SLA. When the SLA recovers, the SD-WAN rule will be used again. Additional detailed testing scenario: SD-WAN self-healing with BGP - FortiGate documentation.